The invention relates to a method for making an electrical connection, and more particularly, to a method of using a glass-ceramic to metal seal for making an electrical connection that is hermetic at elevated temperatures and/or pressures.
Co-axial single pin or multiple-pin connectors featuring hermetic electrical feedthroughs utilize glass for electrical isolation and to form a seal between the metal housing and the metal feedthrough (pin). Robust, hermetic glass-to-metal seals are designed to minimize residual tensile stresses in the glass that arise due to coefficient of thermal expansion (CTE) mismatch between the materials. Common design practice is to minimize the tensile stresses that develop on cooling to temperatures near room temperature. When a glass-to-metal seal is exposed to an elevated thermal environment that can also produce a pressure gradient across the seal, tensile stresses may occur due to the thermo-mechanical strain history of the seal and the CTE mismatch. If glass tensile stresses exceed design limits, cracking can jeopardize seal hermeticity. Geometrical design modifications are one approach to minimize tensile stresses and enhance reliability. Another option is to replace the glass with a glass-ceramic. In addition to increased strength and more refractory behavior of the glass ceramic, its CTE can be altered over a relatively broad range by changes in heat treatment thus allowing the CTE to be a closer match to the CTE of the housing or the pin. Optimization of the glass-ceramic CTE, in conjunction with optimization of design geometry, offers a means to further reduce CTE mismatch-induced residual stresses.
Electrical connectors with hermetic seals are used in aerospace applications, such as communications satellites, microwave communications equip, and military communications and radar systems. A hermetic seal is required for these applications to prevent contamination and corrosion of the electrical connection and other environmentally sensitive components inside the device. Other applications include the use in the automotive industry and commercial communications. Some applications have the potential for harsh operating environments in which the connectors must maintain reliable electrical connectivity and hermeticity. While commercial seal connectors are available that can operate under benign conditions of atmospheric pressure and ambient temperatures, some applications require that hermeticity and electrical connectivity be maintained at both elevated temperatures and pressures The present invention addresses these requirements.